


Chat out of the bag

by Gentlewriter58



Category: Miraculous Ladybug
Genre: Cute Kids, F/F, F/M, M/M, Secrets, Shipping
Language: English
Status: In-Progress
Published: 2020-12-13
Updated: 2021-01-07
Packaged: 2021-03-10 22:33:46
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 4,369
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28054701
Author URL: https://archiveofourown.org/users/Gentlewriter58/pseuds/Gentlewriter58
Summary: Adrien's little sister is finally coming home. Will he be able to keep his secret from a curious five year old or will his secret be discovered?Don't own any of the characters just my OC's. Cross posted on wattpad
Relationships: Adrien Agreste | Chat Noir/Marinette Dupain-Cheng | Ladybug, Plagg/Tikki (Miraculous Ladybug)
Kudos: 17





	1. Chapter 1

Paris, the city of love. A place that was protected by animal themed heroes and besieged regularly by akuma attacks. One said hero was anxiously sitting in his father's office. Adrien, also known as Chat Noir, was trying to think of anything he did wrong to be summoned. His father rarely had time to talk to him face to face so it had to be important.

"Father, you wanted to see me," he said when his father walked in.

"Adrien, I have something important to discuss with you. As you know, your uncle has been taking care of your little sister for a while."

"Since mom has been missing, is Lucia okay?"

Mr. Agreste gave Adrien a look for interrupting him and continued what he was saying. "Your uncle is going abroad for business and he believes that Lucia should be with her family."

"Lucia's coming back home? I've missed her."

His father nodded and proceeded to tell him the details of the smallest Agreste's homecoming.

Adrien was thrilled to hear that Lucia was coming home. After his mom disappeared, his uncle took her in since things were hectic at the time. He hadn't seen her in person since then. They have video chatted but it wasn't the same. His sister should be starting school now.

Once he was in his room, he let his kwami, Plagg, out of his pocket. "So who is this Lucia girl and how come I've never heard of her?" asked the black cat.

Adrien explained to Plagg that his little sister was living with his uncle but was now coming back.

The blonde boy was excited when he got to school. Tomorrow Lucia would be home and things would be a little brighter with her around. 

"Hey Dude, you seem super happy today," noted his friend, Nino. He was sitting at his desk at school waiting for class to begin. 

"Yeah spill," said Alya who was sitting behind him.

Adrien told them his good news and they were shocked to hear that he had a sister. Marinette suggested getting her a gift to celebrate. He thought that was a great idea and texted his uncle to see what kind of things Lucia would like. 

By some miracle, there were no akuma attacks today. He looked at the list of things that his uncle sent.

Lucia's likes:  
Cats  
Superheroes   
Drawing  
Music 

His friends offered to help him find a gift and he actually got permission from his father to go out and get something for her. What would a five year old like as a gift? He didn't think a coloring book or a cd was special enough. Alya suggested Cat Noir merchandise since it was cat and superhero themed. He declined because to him it would be weird for his sister to be wearing his merchandise.

Marinette found a cute charm bracelet that had a cat charm. She said that they could buy more charms for her later. Adrien loved the idea and thought he could buy charms for on special occasions for her.

Back at home, Natalie was waiting for him in the dinning room. "Father is not joining us again." It was more of a statement than a question. 

"There a lot to plan for your sister and for his business. Speaking of which, I called your school and got permission for your sister to stay with you in class. The documents are still processing for her to transferred to her new school," reported Natalie.

"So she will come to school with me tomorrow. Do you think she will be excited to be back home?"

Natalie considered the question and nodded.

"Ugh, children are such a hassle. Now I'm going to have to hide more often," complained Plagg.

"Don't complain. You never met her," chided Adrien.

The cat still complained as he ate his cheese. Adrien rolled his eyes and started on his homework. After he was done, his phone signaled for a video chat. He answered and was met with a cheerful laugh.

"Adrien!" the little girl chirped. 

"Lucia, excited for tomorrow?"

The little girl nodded enthusiastically. His sister inherited their mother's looks. She was her little doppelganger. It hurt a little to see a mini version of her. Maybe that's why their father was okay with her living away from them for so long. He knows it hurts him to be reminded of his wife.

"What's school like? Aunt Marie teaches me here."

"Its fun and you get to come with me tomorrow."

Lucia yawned. "You should go to sleep," said Adrien. The little girl shook her head. "The sooner you go to sleep, the sooner you will see me tomorrow."

She yawned again, "Okay, I love you Adrien."

"Love you too." He turned off the video chat and saw Plagg sticking his tongue out. "I think I have diabetes now with how sweet you two were."

Adrien shook his head in experation, "Good night, Plagg."

"Night," replied the cat.


	2. Chapter 2

Today was the day. Adrien's uncle was dropping off Lucia this morning. Adrien got up earlier than usual. Marinette offered to bring some snacks to school for Lucia so he knew that she would get to eat something sweet. He went home for lunch so that wasn't an issue. He grabbed his present went to the dinning room.

"Adrien, you are up early," remarked Natalie.

"I'm excited to see Lucia again. It's been too long."

"She should be here in a couple of minutes and your father will be down shortly."

"Father is going to join us for breakfast?" Adrien was shocked. His father rarely ate with him. He guessed the incident with Style Queen got to him more than Adrien had thought.

Natalie nodded and let a tiny smile slip. The door bell rang shortly after Natalie left. Adrien walked quickly over to the door since his father would not like him to run in the house. The Gorilla had opened the door and Adrien's uncle, aunt, and Lucia walked in. His uncle was rolling a cute little luggage that had kittens on it. His aunt had a tiny backpack that had a cartoon character on it. Lucia had looked at the front entrance in awe. When she noticed her brother, she dropped the things she was holding and jumped into his arms. 

"Adrien!" 

"Lucia!" Adrian twirled his sister around and held her to his hips. She hugged him and gave him a kiss on his cheek. Their uncle and aunt each gave him a kiss and gushed about how big he was getting. 

While Adrien was talking to their relatives, Lucia wiggled out of his arms, "Papa!" 

She hugged his legs and got a pat on the head. She lifted her hands up to be picked up but was ignored. Gabriel greeted his brother-in-law and his wife. While the adults were talking, Adrien held Lucia again and took her to her room. It was right next to his and was very simple. They would have to decorate it later. The Gorilla carried up her bags. A staff member would unpack her things while they were at school. 

"I got you a gift. Close your eyes." Lucia did as her brother said. He put the little box in her hands. She opened her eyes and unwrapped her present. "For me? I love it." She hugged him and asked him to put it on her. 

The Gorilla came to collect them for breakfast. Their uncle and aunt couldn't stay to eat but kissed everyone goodbye. Lucia sat next to Adrien as she happily talked about everything and anything. When it was time to go, she went up to her papa and gave him a kiss. He kissed her forehead and had a sad smile on his face.

Natalie met them by the car. "I took the liberty of clearing your afternoon schedule so you could have some quality time with Lucia."

Adrien thanked her and Lucia hugged her legs. The ride to school was filled with laughter as Adrien took fun pictures and messed with filters with his sister.

As soon as they got out of the car, Lucia was quiet and hid behind her brother. Adrien held out his hand and she grabbed it. As soon as they entered the classroom a high pitched voice was heard, "Oh Adrikins!" A blonde girl hugged Adrien and nearly made Lucia fall. 

"Careful! Chloe you almost made Lucia fall," said Adrien. 

"Lucia?" She looked at the little girl that she hadn't noticed earlier. After a moment, something clicked in her brain.  
"Omg, Baby Lulu got so big! You obviously remember moi. I mean you are wearing your hair similar to mine."

Adrien classmates went over to see the tiny girl. Everyone was saying how cute she was and how they wanted to hug her.

Lucia did a tiny wave and hid behind Adrian. He took her to his seat since she seemed to be overwhelmed. She hid her face in his arm. 

"Hey little Dudette, would you like to listen to my tunes to feel better?" Lucia lifted her head away from her brother's arm and looked at the boy sitting next to her. She looked at her brother who nodded and she shyly nodded her head. Nino put his headphones on the little girl. They were too big on her but she put her hands on them to keep them still. He selected one of his calming playlists and watched as she closed her eyes. 

Two minutes before class was to begin Marinette rushed into the classroom. "Made it!" She had a bakery box in her hand and she went to sit in her seat but Chloe stuck out her foot to trip her. Marinette yelped and fell on top of the box. "Really, Chloe, you had to trip me. These are sweets for Lucia."

"Whatever, like she would eat the crap you made."

Lucia had taken off the headphones when she saw someone fall. The girl had two pig tails and held the squash bakery box. Her brother had told her about some of his classmates and she remembered a girl who lived at a bakery. She had to be the one. She vaguely remembers Chloe and she did not like that she was being a meanie. She took her hair out of the ponytail so she wouldn't look similar to her.

Marinette sat at her desk and Lucia turned around to see her. "It's nice to meet you, Lucia. I'm Marinette. I had made some snacks for you but now they are a little flat."

The little girl grabbed the box and took a chocolate croissant from it. It was still warm and her face lit up when she took a bite. She broke a piece off for Adrien to try but he told her to enjoy her snack. Marinette passed one to him and he thanked her. Lucia decided that she liked her brother's new friends especially the girl who made yummy snacks.

School went on as normal except for the fact that Lucia didn't speak when she was asked to introduce herself. Adrien introduced her and she worked on her drawings. When gym class was next, Adrien asked if one of the girls could watch Lucia so he could go to the locker room. The girls of the class were happy to watch her since she was so cute. 

Adrien was changing his clothes when Plagg decided to complain about Chloe. "One of these days that girl is going to squish me. Plus she almost ruined the snacks. What if it was cheese?"

"I hate to admit that she has changed. She used to be a sweet girl."

"Well, I'm taking a nap. Don't tiny humans need naps too?" questioned Plagg.

Adrien nodded and went to his gym teacher to see where his sister could take a nap. There was a little couch in the principal's office and he was nice enough to provide a blanket and pillow for Lucia. Adrien had to wonder where they came from but decided that he didn't want to know. 

The rest of the school day went by fast and Lucia was happily showing Adrien the drawings she made. They were pretty good for a five year old. She had drawn some superheroes. She made Ladybug, Chat Noir, Rena Rouge, and Carapace. She gifted him the pictures and gave him another hug. Adrien swore her hugs made everything better.

Lucia happily chatted about the nice people in Adrien class while he worked on his homework. "I like your friends. Nino let me listen to music, Alya let me play on her phone, and Marinette made yummy croissants." 

"I'm glad you like them."

"Can I wear my hair like Marinette tomorrow?"

"Sure, we can do that. You know your hair is longer than hers so it won't look exactly the same."

Lucia yawned and rubbed her eyes. Dinner was good but their father did not come down to eat with them. Adrien lifted her up and took her to her room. He tucked her in and kissed her forehead.

"I thought she would never go to sleep," said Plagg when he came back to his room.

He was eating cheese and floating around, "She is cute though. I can see why you like her."

Adrien went to sleep with a smile on his face. He woke up when he heard someone opening his door. It couldn't be Plagg since he just phases through them. "Adrien? I had a bad dream." A little body climbed into the bed. Adrien maneuvered her so she wouldn't accidently hit Plagg.

She snuggled into his arms and went to sleep. It was one of the best nights of sleep he had in a long time.


	3. Chapter 3

**Summary for the Chapter:**

> The chapter where Gabriel Agreste realizes that little girls can be a handful.

The weekend came quickly and with it came work for Adrien. There had been a couple of close calls with Plagg and Lucia. 

Natalie had told Adrien that Lucia was going to model with him for their father's newest line. He hated that his sister was being forced into modeling. She didn't seem to mind as long as they were together during the shoots. That night, their father had joined them for dinner.

"Lucia, you will start school on Monday. I also enrolled you in gymnastics," said Gabriel. 

"May I have martial arts lessons instead?"

"No, you will be in gymnastics and continue with your violin lessons," replied Gabriel.

With the bravery only a five year old could have, Lucia looked into her father's eyes and said, "No!"

Gabriel was taken back at being argued with. Adrien never talked back to him so this was new to him.

"What did you say young lady?"

Without missing a beat, Lucia said, "No, I want to take martial arts not gymnastics."

"Lucia, you will take gymnastics and you will not raise your voice at me." 

"No!"

They argued back and forth until Adrien intervened, "Father, maybe she could take martial arts on the weekends and her gymnastics during the week."

Natalie quickly pulled up the family schedule and showed it to Gabriel. He scrolled through it and nodded his head.

"Lucia, you will take gymnastics and if you behave we can arrange for martial arts lessons. That means no more temper tantrums young lady."

"Yay, thank you papa!" she went over to him and gave him a kiss.

"I promise to be a good girl." 

With that she went back to eating her dinner like nothing happened.

"Why do you want to take martial arts so bad?" asked Adrien. They were sitting on his sofa watching a movie.

Lucia mumbled something that Adrien couldn't hear. He asked her to repeat herself. "Akuma attacks. I know I can't beat them up like Ladybug and Chat Noir but if I can protect myself then that is one less person they need to worry about."

Adrien ruffled her hair and gave her a kiss on the forehead. They both groaned when his phone reminder went off for piano practice. They stopped the movie and Lucia picked up her violin that she kept in Adrien's room. She liked practicing with him. He chose songs that they could do together so it was more fun.

Half in hour into practice, Adrien's phone went off about an akuma attack. He had to think fast since he couldn't transform in front of his sister. He told her to hide under her bed until he came to get her. When she asked why he told her it was a new safety procedure that the police recommended. She did as she was told and went to her room. Adrien locked his door just in case.

"Coast is clear, Plagg."

"Geez, Hawkmoth had to interrupt just when the music was getting good. Good thinking with your sister by the way. We can't have people knowing your identity."

Adrien sighed. Keeping secrets took a toll on him but he had a job to do. "Plagg, claws out!"

In an instant he transformed into Chat Noir and he leaped through his window to help his lady defeat the current akuma.

Meanwhile Lucia was hiding under her bed. She was watching a live feed of the battle on her phone. She was only supposed to use her phone for emergencies but she considered a bad guy on the loose an emergency. 

The akuma was setting everything on fire. She didn't think that hiding under her bed would protect her from fire so she decided to find Natalie and her papa. They would know what to do in case of a fire.

She knocked on her father's office door and heard footsteps coming towards her. Natalie slightly opened the door. "There's an akuma setting everything on fire. What if it spreads here?"

Natalie took the little girl's hand and took her back to her room. "Everything is going to be okay. We are fully prepared for fires. Your father would never let anything harm you."

She grabbed one of the many stuffed animals in her room and handed it to Lucia. She than called Mr. Agreste on her phone.

"Sorry to interrupt sir but Lucia is scared of the akuma attack. Yes sir thank you sir."

Lucia hugged her toy and looked up at Natalie. "Your father will be here in a moment. "

Gabriel Agreste was secretly Hawkmoth. Natalie was the only person who knew his secret. He was a little annoyed that she had called him when he had Ladybug and Chat Noir on the ropes but she only called him for emergencies. He was doing this for his children and he couldn't have Lucia scared. She might try to find him during akuma attacks and he couldn't have that. 

"Papa!" Lucia shouted as she ran to her father. He lifted her up and she hugged him.

"I heard you were scared about the akuma and the fire coming here," The little girl nodded, "Lucia, I promise you that no akuma will ever harm you while I'm around."

"I love you, papa," she kissed him and he told her to get ready for bed.

Thank goodness for Ladybug's power. Without it Paris would look like a charred wasteland. He fist bumped Ladybug and wasted no time to get back home. Lucia was probably scared and he needed to check on her.

"Sheesh, doesn't Hawkmoth know not to play with fire? I need extra cheese for all the trouble," complained Plagg. Adrien gave him a double helping and went to his sister's room.

"Adrien! Look Ladybug and Chat Noir beat up the bad guy," she said excitedly. She showed her brother the footage on her phone. "If I'm a good girl do you think they will give me their autographs?"

He laughed at his sister's enthusiasm and told her that anything was possible. Maybe he could convince Ladybug to patrol near Lucia's gymnastics class. He kissed her told her that they were going to have fun tomorrow.


	4. Chapter 4

Adrien went back to his room to get ready for bed. He wished Hawkmoth hadn't interrupted his time with his sister. They had been apart for too long and he wanted her to feel safe and happy. 

"I can't believe your science teacher assigned a group project. At least she assigned groups so you don't have to deal with Chloe but still."

"Marinette was kind enough to have us all at her house and I'm sure her family has something with cheese at the bakery."

Plagg rubbed his hands together like a villian when he thought about the tasty cheese. Plus unbeknownst to Adrien he could spend time with his sugar cube. Plagg was too busy plotting and Adrien was too busy putting on his pajamas to notice that Lucia had snuck in his room.

After the akuma attack, Lucia didn't want sleep by herself so she went to her brother's room. "Adrien, Can I sleep --- kitty fairy!"

Adrien and Plagg both froze. "Lucia, that's my new toy from Japan with floating action," he said hastily. Lucia closed the door and went up to Plagg. She pouted at her brother.

"No lying. He's a house spirit like the stories say. You have to be polite to them."

Adrien tried to convince his sister that Plagg was a toy. Finally, Plagg decided to speak, "You are dreaming. This is just a dream. You will wake up in your own bed and bring your brother cheese in the morning."

Lucia giggled, "I like you kitty spirit. My name is Lucia Marie Agreste. Please protect my home."

"My name is Plagg and I am not a minor house spirit. I'm an important Kwami."

Adrien sighed, "Lucia, you cannot tell anyone you saw Plagg."

The little girl nodded. She didn't know what a Kwami was but he looked like a cat so she offered her hand for him to sniff. Plagg refused to sniff her. He looked like a cat but he wasn't a real cat.

The cat kwami was a softy at heart because he let Lucia pet him when she looked sad that he didn't sniff her hand.

"You're a cute kitty, Plagg, and I promise to keep your secret. I'm a good secret keeper because I have a secret that I never told anyone my entire life."

"What secret is that?" asked Adrien.

"If I told you it wouldn't be a secret," she replied as if it were obvious and her brother was silly to ask.

She happily chatted about how much she loved the heroes in Paris especially Chat Noir since he was a kitty and kitties are the best. 

Adrien shot Plagg a look when he had a smug look on his face when he heard how much Lucia loved Chat Noir. 

"Okay, Lucia, it's time for bed now. Tomorrow we get to go to Marinette's house since we have a group project."

"Okay..., I like her. She's sweet and she made me chocolate croissants," she replied with a yawn.

She snuggled in the bed and kissed Adrien good night, "I love you, Adrien. I love you, Plagg."

"I love you too, Lucia."

Soon enough the little girl was fast asleep.

"What are we going to do, Plagg? Lucia knows my secret now!"

"Don't worry about it. She thinks I'm a fairy. So your secret is safe," replied Plagg as he ate some cheese.

When the kwami finished he had a mischievous look on his face. He floated over to Lucia and whispered to her, "When you wake up bring cheese to your fairy guardian. Remember that Plagg likes cheese."

"Plagg, stop sending subliminal messages to Lucia."

The kwami snickered and got comfortable on the pillow between the two Agreste children. Adrien smiled as he looked at them. It was nice not having to hide Plagg and he was glad Lucia liked him. He couldn't remember the last time he felt so happy. 

Adrien woke up to a knock on his door. 

"Adrien, may I come in?"

Plagg hid when he heard the knock so Adrien told Natalie that she could come in.

Natalie walked in and had a tiny smile when she saw Lucia sleeping next to Adrien.

"I supposed Lucia is the reason you slept in this morning."

Adrien explained that Lucia was scared by the akuma and didn't want to sleep by herself.

Natalie nodded and typed something on her phone. She told Adrien that breakfast was ready and after that he would be taken to Marinette's house for his project.

Natalie gently woke up Lucia and took her to her room so she could help her get dressed.

Lucia came down to breakfast wearing a cat ear headband and a pink dress with paw prints at the bottom. Their father was absent yet again but Adrien was used to it. As soon as they finished breakfast, Lucia ran off to get her things together. Adrien got his school stuff together and made sure Plagg had his morning cheese. 

"Adrien, Adrien, look! look!" Lucia ran into his room and showed him her kitty backpack. She took out a metal pencil case but instead of pencils, she put little pieces of cheese wrapped in napkins in it. "Plagg said he likes cheese so I took a little bit of cheese from the kitchen when the staff wasn't looking."

Plagg came out of Adrien pocket when he heard the word cheese.

"She is now on my list of favorite humans and on the kwami protection list."

"Really!?" said Adrien and Lucia at the same time. Adrien in disbelief and Lucia in pure happiness.

"You are now my favorite pair of cheesy siblings."

Lucia cheered and Adrien shook his head at his kwami. 

"Adrien, Lucia, if you two don't leave now, you will be late. Your father will not be happy if your school work suffers."

Lucia opens her backpack and asked Plagg if he wanted to stay with her for the ride over. Plagg looked over to Adrien to see if he was okay with that plan. Adrien nodded and the cat kwami made himself comfortable in the cute backpack.

Today will be a good day because Lucia had her big brother and a kwami on her side. 


End file.
